A lithium ion secondary battery is excellent in an energy density and has been spreading for a portable apparatus and the like. As the lithium ion secondary battery, batteries, in which a laminated film is used for an exterior packaging member, have been put into practical use because the energy density of the batteries is high at a light weight and the batteries can be manufactured in a very thin shape.
In batteries such as the lithium ion secondary battery in which the laminated film is used as the exterior packaging member, an electrolytic solution and a polymer compound are used as an electrolyte so as to obtain liquid leakage resistance and the like, and the batteries are known as polymer batteries. Among these batteries, a gel electrolyte battery, in which an electrolytic solution is retained by a polymer compound and has a so-called gel shape, is widely spread.
As a technology related to the gel electrolyte battery, Patent Document 1 suggests a configuration in which a resin is applied to a surface of a separator. Patent Document 2 suggests a configuration in which alumina particles and the like are mixed in the gel electrolyte to improve the strength of the gel electrolyte.